Trussed structural member and method of and means for its manufacture



June 24, 1941. 5 DE SALARD] 2,246,578 TRUSSED STRUCTURAL MEMBER ANDMETHOD OF AND MEANS FOR ITS MANUFACTURE Filed Feb. 24, 1939 5Sheets-Sheet l ,2 'Fi 1' 6 rigzfzgz A 1 J 6 I INVENIOR June 24, 1941. I5, DE RD 2,246,578- TRUSSED STRUCTURAL MEMBER AND METHOD OF AND MEANSFOR ITS MANUFACTURE Filed Feb;'24, 1939 s Sheets-Sheet 2 g mu Z H: I:E1: g; rw

June 24, 1941. A." B. DE SALARDI 2,246,578

TRUSSED STRUCTURAL MEMBER AND METHOD OF AND MEANS FOR ITS MANUFACTUREFiled Feb. 24, 1959 3 Sheets-Sheet s ,5 M ,MW 15- 4! INVENTOR V arrearsivmuou or sun UFAE TUMtlE LTPRHJSSE STRWGTML E dlhert Bernhard Salardi,Wilkiusbg, li e Application ll ebruary 24; rest, semi No. esaeso 22illaims.

(hereinafter called conventional) consist of" one or more bars(hereinafter called "parent bars) of substantially uniform crosssections thruout their length integral and forming certain angles witheach other and'distinguished,

according to location, by such names as:

Subjected to bending forces the conventional structural members do notutilize their material in the most eflicient way because the materialtoward the neutral axis participate only to a relatively small extentinthe development of the stresses which are needed to balance the act.-ing iorces while in the same time the fibres -remotest from the-neutralaxis may be stressed beyond their elastic limits. This unequaldistribution of the stresses necessitates an increase of the crosssectional area hence the useof a heavier member for supporting a certainload. My invention does away with above and other drawbacks by providingan improved distribution of the material bounded by the cross sectionsso that the stresses are more evenly developed thruout the crosssections, the buckling effects in the web portions are reduced, thestrength and rigidity of the member substantially increased andapproximately the maximum economy-in to provide structural membershaving relatively thin and wide indented parent bars carrying a networkof integral derivative bars protruding. therefrom with a height. that isgreater than the minimum thickness or the indented parent bar forincreasing the strength, stifiness and economy of the member; firth, toprovide structural members having cross sections of greater momenta( ofinertia and radii of gyration, respectively, thanthose of theconventional members of equal cross sectional areas; sixth, to providefabricated structural members composed oi at least one member havingderivative bars facilitating rigid attachment by welding; seventh, to

provide structural members having an increased members by rollingconventional structural memmaterial can be achieved under the givencircumstances. I achievethese purposes by providing parent bars ofthemember with pockets or indentions bounded by derivative bars (thesebars derive their material from that replaced by .the' pockets)protruding from the parent bar,

integral therewith and forming triangles constituting at least one rigid(non-collapsing) truss embossed upon the surface thereof.

Hence, the objects of my invention are: first, to providestructuralmembers parent bars of which having sunk-in pockets' or indentionsbounded by derivative bars arranged'in a. netbers and subsequentlyproducing on its parent bars indentions or sunk-m pockets and protrud-'ing derivative bars by dierolling; ninth, to provide a method ofproducing improved structural members adding to the rolling. die rollingof the member, respectively, some or all of the steps of longitudinalcutting, bending and partial or total progressive reheating thereof;tenth, to pro- .vide means for manufacturing the improved structuralmembers comprising a rolling mill having flat-rolling and onedie-rolling passes the latter being formed by rolls at leastone or whichis'p'rovided with a network of connected grooves arranged in atriangular pattern; eleventh, to

provide means for manufacturing the improved structural memberscomprising a rolling mill having flat-rolling, die-rolling and bendingpasses and some or all of the following means shaping. operations.

work of triangles integral with and protruding substantially from theparent bar; second, to provide structural members having the parent barswith a network of derivative bars embossed thereon, said derivative barsforming rigid trusses; third, to provide structural members in whichportions at varying distances from the neutral axis are rigidlyconnected by derivative bars protruding from the parent bar; fourth,

These and other ancillary objects as well as the various improvementsand advantages of my invention will be best-understood by reading thefollowing specification in conjunction with the accompanying drawings.in which:

Fig. 1 is the plan view of one embodiment of the invented structuralmember: a trussed plate;

Fig. 2 is a cross sectional view on the line IIII of Fig. 1;

Fig. 3 is the sectional view of an one side trussed plate;

Fig. 4 is the side elevational view of another embodiment showing atrussed L-beam havin sunk-in pockets and derivative bars on both flangesand the web;

Fig. 5 is a sectional view taken on the line v v of Fig. 4;

Fig. 6 is the top plan view of the trussed I- beam shown in Fig. 4;

Fig. 7 is the side elevational view of another trussed I-beam in whichthe thickness of the web and the width of its derivative bars areincreasing toward the neutral axis;

Fig. 8 is a sectional view taken on the line VIII-VIII of Fig. 7; 4 Fig.9 is a cross sectional view of a trussed structural member having apartially closed or semi-closed box shape obtained from a trussed plateby bending;

Fig. 10 is a partial cross sectional view of an exemplary embodimenthaving an open channel shape obtained from a trussed plate by bending;

Fig. 11 is a sectional View of a trussed channel taken on the line Xi-XIof Fig. 12; v

Fig. 12 is the side elevational view of a trussed channel;

Fig. 13 shows in diagrammatic plan view the apparatus for slitting atrussed plate longitudinally into several narrower strips;

Fig. 14 is a partly sectional view taken on the line XIV-XIV of Fig. 13;

Figs. 15, 16, 17 and 18 show diagrammatically the apparatuses andoperational steps necessary to produce from a trussed plate asemi-closed box shaped member by bending;

Fig. 19 is the diagrammatic plan view of the apparatus for producingsemi-closed box shaped trussed structural members by fiat rolling anddie rolling and bending;

Fig. 20 is a fragmental cross sectional view of a composite structureobtained by welding to a trussed structural member other members,conventional or trussed;

Fig. 21 illustrates diagrammatically the apparatus producing trussedstructural members;

Fig. 22 shows diagrammatically the die rolls of a die rolling passproducing trussed I-beams;

Fig. 23 is the diagrammatic plan view of the apparatus producing trussedstrips by cutting longitudinally a wide trussed plate;

Fig. 24 is a diagrammatic partial sectional view of the reheatingapparatus for reheating portions of the structural member during therolling operations;

Fig. 25 is the. diagrammatic plan view of the apparatus for rolling anddie rolling a wide trussed plate and cutting and bending it forproducing simultaneously several trussed structural members.

Referring closer to the'drawings by the characters of reference in Figs.1 and 2 the shown embodiment of my invention is a trussed platedesignated generally by 2. It comprises the web or the indented parentbar 4 and the derivative bars 6, 8 and I0 raised on one side of the weband 6', 8' and ID on its other side. The derivative bars are integralwith'the indented parent bar and with each other, 6, 8, 6 and 8 runninglongitudinally (referred to as the bases), I0 and I0 running diagonally(referred to as the struts) of the member. The network of the derivativebars shows equilateral triangles raised on the surface of the indentedparent bar 4 constituting a number of connected Warren type trusses.Though the type of the truss in the pattern of which the derivative barsare arranged is optional I prefer the Warren type truss pattern in whichthe'struts form equal angles A with the bases and I also prefer tochoose A so that it satisfies the following equation:

tan. A T

where C is the crushing strength and T is the tensile strength of thematerial of the structural member. In case of commercial low carbonsteel the approximate value of A in degrees will be 52.

It was shown by calculus that an equilateral triangular frame having twobase-angles A satisfying above equation will need to have the leastweight to support .a certain load, hence this construction will lead tothe greatest economy when incorporated into my trussed structuralmembers.

In case the trussed plate is intended to be cut or bent along the middleof a longitudinally running derivative bar, Iprefer to make some of suchbars twice as wide than the others along which such operation is notintended.

The original cross sectional dimensions of the conventional parent barare shown in Fig. 2 by dot and dash lines illustrating the reduction ofthe thickness to that of web 4 bythe indentions and the protrusion ofthe derivative bars from the indented web to a height which ispreferably greater than the minimum thickness of the indented web. Withother words, in all embodiments of the invented trussed structuralmembers I segregate the material, displaced in the parent-bars byindentions, into derivative bars, which protrude therefrom above theoriginal surface of the parent-bar, the latter being shown in Figs. 2and 3 in dot and dash-lines.

Fig. 3 is a cross sectional view of a similar embodiment representing aone side trussed plate, the derivative bars 6", 8 and I0" being raisedonly on one side of the web 4 which is shown to be flat on one face andconvex between the derivative bars. The cross sectional dimensions ofthe original conventional plate are shown in dot and dash lines.

Generally, the thickness of the bars at the indentions is kept at aminimum determined by the necessary strength and limitations imposed bythe manufacturing process and by the physical properties of the materialwhile the derivative bars are preferably made to have proportionate butsubstantial cross sections for substantial increase of the rigidity andeconomy of the member.

As the trussed members are preferably shaped by rolling, the profiles ofall derivative bars and those of the corresponding grooves in the dierolls will consist of suitably curved surfacessome of them similar togear-teeth flanksmerging through fillets of proper radii into thesurfaces of the indented parent bar. As the determination of such curvedsurfaces is a matter of skill only, I do not describe or show them moreparticularly.

Figs. 4, 5 and 6 illustrate another embodiment of my invention, atrussed I-beam I5 upon the indented parent bars of which integralderivative bars are raised arranged in networks of triangles formingrigid (non-collapsing) trusses. In the exemplary embodiment shown eachflange [6 of the I-beam I5 is provided with outwardly protruding trussesl8 and the web 20 with trusses 22 raised thereon on both sides, eachtruss being formed by derivative bars. The trusses shown aresubstantially of the Howe type, but any other type of rigid network oftriaaeams angles will be satisfactory. I recommend also in thisembodiment the employment of the Warren trusses with base anglessatisfying the aforementioned equation for increased economy. As thispattern is illustrated in 'Fig. 1 it is not necessary to repeat it.

In the embodiment shown the parent flanges are wider than the trussesformed thereon so that protruding lips M remain which due to theirsmaller mass are especially suited for quick welding to other membersforming fabricated structures; they have also a value as convenientsupport of added members before welding. An exemplary embodiment ofsuchcomposite welded structure is shown in Fig. 20.

Figs. 7 and 8 illustrate'a trussed I-beam l which differs from thatshown in Figs. 4 to 6 in so far only that the thickness of the web 20'and the width of the derivative bars forming trusses 22' are increasingtoward the plane of the neutral axes of the cross-sections and that theflanges and their trusses are shown to be coextensive and no lateral lipis formed. It is obvious that the lips may be added to this or any otherembodiment of trussed structural members and also, that the width andthe height of the derivative bar's aswell as the thickness of theindented bar may be varying instead of being substantially constant,asshown in the majority of the illustrated embodiments.

Fig. 9 is the cross sectional view of a semiclosed box-shaped trussedstructural member 44 made from a trussed plate of suflicient width bybending it about four axes X, Y, U,- and V running in the longitudinaldirection of the member. 4

Fig. 10 is a partial cross-sectional view of an I open channel-shapedtrussed structural member 45 obtained from a trussed plate of suflicientwidth by bending said plate about four axes, running in the longitudinaldirection of the member. Of these four axes only two, X and U are shown.The embodiments shown in Figs. 9 and 10 are especially adapted forreinforcing concrete structures cast about them.

7 Figs. 11 and 12 illustrate a trussed channel 34 the flanges and theweb of which being provided with indentions and derivative bars formingtrusses 36, 38 and 40. The trusses are narrower than their flangesleaving laterally protruding lips 42 in the preferred embodiment.

Figs. 13 and 14 illustrate diagrammatically the grooved rolls 5% and Gilshown broken away. The

apparatus for dividing a trussed plate such as 2 I in Fig. 1 into anumber of strips. The plate 2 is led onto rotary slitting shear 48 ofany approved design having cooperating shear disks 5" and W that cut theplate 2 into strips 2a, 2b and 2c. Adjusting laterally the positions ofthe disks by known means (not shown) the width ,of the strips arecontrolled.

Figs. 15 to 18 illustrate the apparatus for and method of, respectively,bending a trussed plate by rolling it through suitable roll-passes intodifierent shapes such as angles, channels, semiolosed box, etc.

Fig. 15 shows the bending of the cut strips (only 20. and 2b are shown)by a roll-pass formed by suitably profiled rolls 54 and 56 shown brokenaway. The bending of the strips is effected at an acute angle,preferably about 45 around longitudinal axes U and Y corresponding tothose shown in Fig. 9.

Fig. 16 illustrates'the completionofthebending of the same strips aroundthe sameaxes to apparatus producing trussed plates.

resulting shape is a U channel.

' Fig. 17 shows the bending of. the channel formed of strip to aboutlongitudinal axes X and Y in a third roll-pass constituted by suitablyprofiled rolls 62 and 6% shown broken away. The bending is efiected atan acute angle, preferably 45". 7

Fig. 18 shows the last bending operation for obtaining the semi-closedbox shape 4% (shown to a larger scale in Fig. 9) completing the bendingabout axes X and Y to 90'. This final bending is efiected by a suitablygrooved roll 66 of relatively large diameter (shown broken away) and twoor'more cooperating mandrel-rollers 6t rotatably mounted on a stationarybracket ill accommodated in the groove of the large roll.

In Figs. 13 to 18 conventional (solid) plates are shown for simplicitybut it will be understood that they may also represent trussed plates.Full lines illustrate the obtained shapes after they leave therespective roll-pass, dot and dash lines the previous shape-5,. beforeentering the respective pass.

Fig. 19 illustrates diagrammatically the apparatus for producingsemi-closed box-shaped trussed structural members 44 (shown in Fig. 9)by rolling. The trussed plate 18 is led onto four consecutive bendingpasses, corresponding to those shown in Figs. 15 to 18, of which passesonly the first and the last ones are indicated by rolls 54 andlifi'respectively, the second and third passes being broken away in thedrawings. 'H is the last finishing stand of a hot-strip orplate-milldelivering the parent-bar or plate 12 onto the die-rollingstand 13 having a roll pass formed by a set of rolls at least one ofwhich is a die-*roll l4 producing from the parent-plate the trussedplate 18. reheating devices 80 are installed for continuous andprogressive reheating of the work-piece which travels through them. Thedie-roll l4 that some or all of them may be of the invented trussedtype.

Fig. 21 is the diagrammatic plan view of the finishing stand llrepresents a not strip mill delivering the parent bar or plate I2 ontothe dierolli ng stand lthaving a pass formed by a set of rolls at leastone of which is a die roll It provided with suitable grooves 15corresponding to the desired derivative bars 15 to be raised on theparent plate for producing the-trussed plate 18 delivered from the dierolling stand in the direction of the arrow. .80 is-a suitable heatingdevice of any approved design'located between the finishin pass and thedie rolling pass for reheating the moving plate to the desiredtemperature previous to die rolling. The reheating device 80 is shownbroken away; its design, dimensions and control are such that the plate,

9W in a succeeding roll-pass formed by suitably traversing it,with thespeed of the mill, is kept Between the roll passes The last and 920bybending.

automatically within the desired temperature limits.

Fig. 22 shows diagrammatically the die-roll pass and the die-rolls(broken away) for producing trussed I-beams such as illustrated in Figs.4 to 8. The die-roll pass is formed by two horizontal die-rolls 82 and84 and two vertical die-rolls 86 and 88 the axes of which are preferablyin the same vertical plane. In case any of the trusses should be omittedthe respective die-roll would have to be replaced by a smooth surfacedroll. I am using the expression dieroll to designate a roll carrying onits body dieblocks having the shape of substantially truncated pyramids,with curved side surfaces protruding from the cylindrical base of therollbody and forming peripherally widening grooves between the dieswhich grooves are the molds of the derivative bars into which thedisplaced material is squeezed during die-rolling.

By substituting in Fig. 21 in place of stand II a universal mill standand for the die-rolling pass that illustrated in Fig. 22 we obtain theapparatus for rolling trussed I-beams.

Fig. 23 illustrates diagrammatically the apparatus for producing widetrussed plates and subsequently cutting them into narrower strips. It isa combination of the apparatus shown in Fig. 21 and the rotary slittingshear illustrated in Figs. 13 and 14. The conventional solid rolledplate 90 enters the die-rolling stand I3 having sufliciently wide dierolls I4 and is shaped into trussed plate 92 which is then deliveredonto rotary slitting shear 48 to be divided into strips 92a, 92b and 920by the action of the shear disks 50 and 52. Finishing stand IIrepresents a hot plate mill and 80' a suitable reheating device.

Fig. 24 is the cross sectional view of a heating device 80 representedin a semi-diagrammatic manner. It comprises a chamber 94 of heatinsulating material enclosed preferably in a metallic shell 96 andhaving suitable openings 98 for receiving and delivering the workpieceand admitting burners I which eject blasts of combustion gases impingingupon the workpiece 90 moving through the chamber and supported byrollers I02 rotatably mounted and preferably water cooled. I04 is thepiping for the cooling water and I06 the driving connection of therollers. The burners I00 are arranged in sufficient number at properlocations to elevate the temperature of the workpiece and keep itbetween desired limits.

The mixture of the'combustion gases and the intensity of the blastsejected by burners I00 are automatically regulated by known means (notshown) for conveying suificient heat to the moving workpiece the massand the speed of which being varied between predetermined limitsaccording to need. The control means may enable the uniform. heating ofthe whole plate or selectively intensified heating of certain stripsonly, according to need for cutting or bending the workpiece alongcertain lines,

The reheating devices may also be electrical ones such as showndiagrammatically in Fig. 25 which is a schematic plan view of theapparatus for producing simultaneously a number of trussed channels,formed from strips 92a, 92b The bending roll passes are indicated byrolls 54 and 58 already described in Figs. and 16. The reheating devices80 are shown to use electrical energy for heating,the transformation ofthe energy being effected by known means of electric resistance orelectromagnetic induction, not shown.

In Figs. 19 and 25 the network of grooves of the die rolls I3 and I3 areindicated schematically by a network of lines.

Having fully described my invention and illustrated certain preferredembodiments thereof, it will be understood that various changes andalterations may be made by those skilled in the art in practicing myinvention without departing from the spirit and the scope thereof, henceI do not wish to be limited by the shown illustrative embodiments, butwhat I claim as new and desire to protect by Letters Patent is:

1. Trussed structural member comprising a plurality of substantiallyprismatic parent bars united longitudinally throughout their lengthforming predetermined angles with each other and derivative integralbars embossed upon said parent bars in patterns of composite triangles,said derivative bars constituting in themselves a plurality of rigidtrusses arranged to each other at the same angle as said parent bars.

2.. Trussed structural member comprising a plurality of substantiallyprismatic parent bars united longitudinally throughout their lengthforming predetermined angles with each other and integral derivativebars embossed upon said parent bars in patterns of composite isocelestriangles the equal legs of which form an angle of A with theirrespective bases, said derivative bars constituting in themselves aplurality of rigid Warren type trusses arranged to each other at thesame angle as said parent bars, said angle A satisfying the equationtanA= where C denotes the crushing strength and T denotes the tensilestrength of the material of said member at ordinary temperature to whichit is subjected during use.

3. Trussed structural member comprising a plurality of substantiallyprismatic parent bars united longitudinally throughout their lengthforming predetermined angles with each other and derivative integralbars embossed upon said parent bars in patterns of composite triangles,said derivative bars constituting in themselves a plurality of rigidtrusses arranged to each other at the same angle as said parent bars,the width of some of said trusses being less than that of the respectiveparent bar having lateral strips free from said derivative bars.

4. Trussed structural member according to claim 1 in which said parentbars form an angle of with each other constituting a plate.

5. Trussed structural member according to claim 1 in which three parentbars are arranged in an I shape, two of said parent bars forming theflanges and the third being the web of said I shape.

6. Trussed structural member according to claim 3 in which three parentbars are arranged in an I shape, two of said parent bars forming theflanges and having lateral strips free from said derivative bars and thethird of said parent bars forming the web provided with derivative barsextending all over its width.

7. The method of producing trussed structural members consisting in thesteps of hot rolling the work piece into a shape composed of prismaticparent bars of suitable dimensions and being united longitudinallythroughout their ranged to each other at the same angle as said parentbars.

t. The method of producing trussed structural plates consisting in thesteps of hot rolling the Work piece into a plate of suitable dimensionsand subsequently die-rolling it in a manner that substantiallytriangular indentions are obtained therein and the squeezed-awaymaterial is segregated into derivative bars surrounding said indentionsand arranged in patterns of composite triangles forming in themselves aplurality of annexed rigid trusses.

9. The method of producing trussed structural members consisting in thesteps of hot rolling the work piece into a plate of sufiicientdimensions, afterwards die-rolling it in a manner that substantiallytriangular indentions are obtained therein and the squeezed-awaymaterial is segregated into derivative bars surrounding said indentionsand arranged in patterns of composite triangles forming in themselves aplurality of annexed rigid trusses and subsequently subjecting thedie-rolled plate to permanent dewidening grooves arranged in a patternof comformation chiefly by bending, preserving sub- 11. The method ofproducing trussed structural members consisting in the steps of hotrolling the work piece into a plate of suitable dimensions andsimultaneously progressively reheating and die-rolling it in a mannerthat substantially triangular indentions are obtained thereon and thesqueezed-away material-is segregated into derivative bars surroundingsaid indentions and arranged in patterns of composite triangles formingin themselves a plurality of annexed rigid trusses and subsequentlysubjecting the die-rolled plate to progressive permanent deformationchiefly by bending, preserving substantially the values of the areas ofthe cross sections obtained by die-rolling.

12. A rolling mill comprising a finishing roll pass containing at leastone roll having on its body portion a network of communicatingperipherally widening grooves arranged in a pattern of compositetriangles constituting the negatlve imprint of the bars of a rigid trussbent about a cylindrical surface and adjacent to said die roll pass a.reheating device through which the workpiece passes on its way towardsaid die roll pass for progressive increase of its temperature andplasticity to facilitate the dierolling.

13. A hotplate mill comprising a die roll pass containing at least oneroll having on its body posite triangles constituting the negativeimprint of the bars of a rigid truss bent about a cylindrical surface,adjacent. to said die roll pass a reheating device through which theworkpiece passes on its way toward said die roll pass for progressiveincrease of its temperature and plasticity to facilitate thedie-rolling, and bending roll passes following said die roll pass forprogressive permanent deformation of the die-rolled plate by bending.

14. For deforming material in plastic state, i

a die-roll having neckand body portions, the latter consisting of asubstantially cylindrical base and a plurality of die-blocks integralwith and protruding radially from said such a shape that theplan-projection of the sectional areas of each with said base and alsowith other coaxial cylindrical surfaces within the periphery of 'saidbody-portion are substantially triangular with rounded-off corners, thedimensions of said sectional areas decreasing with the increase of thediameters of said cylindrical surfaces.

15. A rolling millgcomprising a die roll pass containing at least onedie-roll having a body portion consisting of a substantially cylindricalbase and a plurality of die-blocks integral with and protruding radiallyfrom said base in such a shape that the plan projection of the sectionalareas of each with said base and also with other coaxial cylindricalsurfaces within the periphery of said body portion are substantiallytriangular with rounded off corners, the dimensions of said sectionalareas decreasing with the increase of the diameter of said cylindricalsurfaces, and adjacent to said die roll-pass a reheating device throughwhich the workpiece passes on its way toward said die roll-pass forprogressive increase ofits temperature and plasticity to facilitate thedie rolling.

16. A hotplate mill comprising a die roll pass containing at least onedie-roll having a body portion consisting of a substantially cylindricalbase and a plurality of die-blocks integral with.

and protruding radially from said base in such a shape that the planprojection of the sectional areas of each with said base and also withother coaxial cylindrical surfaces within the periphery of said bodyportion are substantially triangular with rounded off corners, thedimensions of said sectional areas decreasing with the increase of thediameter of said cylindrical surfaces, adjacent to said die roll pass areheating device through which the workpiece passes on its way towardsaid die roll pass for progressive increase of its temperature andplasticity to facilitate the die-rolling and bending roll-passessucceeding said die roll-pass for progressive permanent deformation ofthe finished plate by bending.

17. For deforming material in plastic state, a

" die-roll having neck and body portions, the latter consisting of asubstantially cylindrical base and a plurality of die-blocks protrudingradially from said base, said die-blocks forming substantially truncatedpyramids with curved side-surfaces having finit radii of curvature.

18. A rolling mill comprising a die-roll-pass containing at least onedie-roll having a body portion consisting of a substantially cylindricalbase and a plurality of die-blocks'protruding radially from said base,said die-blocks forming substantially truncated pyramids with curvedside-surfaces having finit radii of curvature.

portion anetwork of communicating perip y W 19. A hot-plate-millcomprising a die-rolling base in pass containing at least one die-rollhaving a body portion consisting of a substantially cylindrical base anda plurality of die-blocks protruding radially from said base, saiddie-blocks forming substantially truncated pyramids with curvedside-surfaces having finit radii of curvature and at least one bendingroll pass for progressive permanent deformation of the die-rolled plateI by bending. 20. The method of producing structural members havingsemi-closed box-shape consisting of the steps of rolling plates andprogressively subjecting said plates to permanent deformation by bendingwithout substantially altering the cross sectional areas ofthe-work-piece.

ALBERT BERNHARD DE SALARDI.

